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api-breaking-change-detector

Cross-references C# Web API controllers/DTOs against their TypeScript/JavaScript consumers (React, Angular, Vue, Svelte, Node.js, or hand-written/auto-generated HTTP clients like Fetch, Axios, NSwag) to catch contract drift in both directions: backend changes that break client applications (renamed/removed JSON keys, new required parameters, status code shifts) and frontend code sending fields the backend no longer reads. Works directly against source code, not exported OpenAPI spec files. Use when the user asks to check for breaking API changes, verify frontend/backend contract sync, or audit a DTO/controller change against its TypeScript/JS consumers before merging. Not for generating new API code from a spec (see openapi-to-application-code) or scaffolding new endpoints (see aspnet-minimal-api-openapi).

Quality

87%

Does it follow best practices?

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SecuritybySnyk

Passed

No findings from the security scan

SKILL.md
Quality
Evals
Security

Quality

Content

75%Weight 40%Scale 1-5

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

A solid, actionable instruction-only skill body: a clear six-step audit workflow, concrete attribute and normalization specifics, and a well-defined output format. Main weaknesses are minor duplication between Process and Guidelines, LaTeX-arrow formatting artifacts, and no explicit findings-verification step before reporting.

Suggestions

Remove the 'Naming Policies' and 'URL Normalization' Guidelines bullets that restate Process steps 1 and 3, keeping each rule in one place.

Replace the literal "$\rightarrow$" LaTeX artifacts with plain "→" or "->" so the markdown renders cleanly.

Add a short verification step (e.g. re-confirm each finding against the matched source lines) before producing the report, and consider moving the detailed route-normalization matching rules into a one-level-deep reference file.

DimensionReasoningScore

Conciseness

The body assumes domain competence (no explanations of what ASP.NET Core, fetch, or axios are) and stays lean, but the Guidelines "Naming Policies" and "URL Normalization" bullets substantially restate Process steps 1 and 3, and stray LaTeX artifacts ("$\rightarrow$") add noise. Not 5: the duplication and formatting artifacts are trimmable; not 3: the rest is efficient with only minor over-explanation.

4 / 5

Actionability

Gives concrete attribute-level guidance ([JsonPropertyName], [BindRequired], C# 11 required, [ProducesResponseType]) and concrete normalization examples ("${this.apiUrl}/users/${id}" → "/users/{id}"). Not 5: it is instruction-only (reporting-only skill, so no code is fine), but lacks concrete discovery commands or patterns for locating consumers (e.g. grep/ripgrep patterns), leaving minor gaps.

4 / 5

Workflow Clarity

Six clearly sequenced steps (naming policies → contract surface → consumer matching → both comparison directions → report) with a "report as 'no client consumer located' rather than guessing" checkpoint. Not 5: there is no explicit verification pass over accumulated findings before producing the report; not 3: the sequence is complete and checkpoints for the risky guess-step are present.

4 / 5

Progressive Disclosure

Well-organized sections (When to use / Process / Output Format / Guidelines) with no bundle files to reference, so the single-file structure is appropriate. Not 5: the body is ~70 lines (above the under-50-line simple-skill exception) and the detailed URL/route matching rules and output-format details are candidates for a one-level-deep reference file.

4 / 5

Total

16

/

20

Passed

Description

92%Weight 40%Scale 1-5

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

An excellent description: specific, bidirectional statement of what the skill does, explicit and varied use-when triggers, third-person voice, and explicit negative scoping against adjacent skills. Its only weakness is slight verbosity and a few missing natural synonyms, which keep trigger-term quality at the near-top level.

DimensionReasoningScore

Specificity

"Cross-references C# Web API controllers/DTOs against their TypeScript/JavaScript consumers" with concrete drift examples ("renamed/removed JSON keys, new required parameters, status code shifts"; "frontend code sending fields the backend no longer reads") lists multiple specific actions with comprehensive bidirectional coverage. Not 4: there are no material gaps in the action coverage.

5 / 5

Completeness

Explicitly answers both what ("Cross-references... to catch contract drift in both directions") and when ("Use when the user asks to check for breaking API changes... before merging"), with concrete trigger phrases. It even adds negative scope ("Not for generating new API code from a spec"). Matches the top anchor; not 4 because the 'when' clause is explicit and specific rather than improvable.

5 / 5

Trigger Term Quality

Includes natural trigger phrases ("check for breaking API changes", "verify frontend/backend contract sync", "audit a DTO/controller change") plus broad technology vocabulary (React, Angular, Vue, Svelte, Node.js, Fetch, Axios, NSwag). Not 5: a few natural user phrasings (e.g. "will this break the frontend", "Swagger", ".NET") are absent, leaving keyword coverage just short of fully comprehensive.

4 / 5

Distinctiveness Conflict Risk

"Works directly against source code, not exported OpenAPI spec files" carves out a clear niche, and explicit disambiguation against named sibling skills ("see openapi-to-application-code", "see aspnet-minimal-api-openapi") minimizes wrong-skill triggering. Not 4: the overlap risk with related spec-based skills is explicitly addressed, not merely minor.

5 / 5

Total

19

/

20

Passed

Validation

100%

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 16 / 16 Passed

Validation for skill structure

No warnings or errors.

Repository

github/awesome-copilot

Path

skills/api-breaking-change-detector/SKILL.md

Reviewed

Table of Contents

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